The present invention relates to a diagnostic method of equipment and a system using the same for separating a failed portion in a communication line apparatus such as a digital switching equipment or a digital cross-connect equipment.
In a digital switching equipment or a digital cross-connect equipment, when a failure occurs in the equipment, a diagnosis of the equipment is effected to separate the failed portion thereof. For example, as described in the "Digital Synchronous Terminal System for Inter-City Network: &lt;Series 2&gt;" on pages 95-106 of the Japanese periodical "Shisetsu (Facilities)", Vol. 33, No. 11, there has been a method of separating a failed highway in which filling time slots on highways are utilized to insert and to check test signals in the equipment. The diagnostic method will now be described with reference to a block diagram of FIG. 4 and a flowchart of FIG. 5.
As can be seen from FIG. 4, the diagnostic method is applied to an equipment comprising a time division switch 1, a multiplexer 2, a demultiplexer 3, receiving circuits 4-5 respectively including test signal generators 11-12, transmitting circuits 6-7 respectively including error detection circuits 13-14, a switch controller 8, and an equipment diagnostic section 9. In the receiving circuits 4-5, input signals received are converted into sub-highway frames suitable for switching operations and inserts a specific pattern generated by the test signal generator 11 or 12 into a filling time slot, thereby delivering the resultant signals to the multiplexer 2. The multiplexer 2 effects a multiplexing operation on two sub-highways to configure a high-way, thereby outputting the signals to the time division switch 1. The time division switch 1 exchanges the time slot of the primary signal under the control of the switch controller 8. The time slot into which the test signal is inserted is not to be exchanged or to be exchanged constantly. In the demultiplexer 3, the highway is demultiplexer into two sub-highways again. The transmitting circuits 6-7 output primary signals to external devices and checks at the same time the test signal on the filling time slot by means of the error detection circuits 13-14. An error thus detected here is sent to the equipment diagnostic section 9. In the equipment diagnostic section 9, as shown in the flowchart of FIG. 5, when an error is detected, the location where the error has occurred is predicted depending on a combination of error detecting positions.
For example, assume that an output from the test signal generator 11 is fixedly connected to the error detection circuit 13 and that an output from the test signal generator 12 is fixedly fed to the error detection circuit 14. If the error detection circuit 13 detects an error and the error detection circuit 14 does not detect an error, the equipment diagnostic section 9 recognizes that the error has occurred in a sub-highway interval, namely, in an interval between the receiving circuit 4 and the multiplexer 2 or between the demultiplexer 3 and the transmitting circuit 6. Furthermore, in the case where the error detection circuits 13-14 respectively detect errors, the equipment diagnostic section 9 judges that the failure has occurred in a highway interval, namely, in an interval between the multiplexer 2 and the demultiplexer 3.
In this method, since the filling time slot into which the test signal is inserted is fixedly connected as described above, the number of error detection points must be increased to improve the precision of the separation of the failed portion.